JP2010262160A - Conductive rubber roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive rubber roller which is not easily permanently deformed (low compression set), has low-hardness, which does not easily soil another member coming into contact with it and at the same time is excellent in extrusion properties. <P>SOLUTION: The conductive rubber roller comprises a conductive rubber layer arranged on the outer circumferential surface of a conductive axial body, wherein the conductive rubber layer is made of a rubber composition including components (A) to (C) below. (A) component: 100 pts.mass of rubber component containing at least 0.5-15 mass% of crystalline butadiene resin, (B) component: 10 to 60 pts.mass of filler, and (C) component: 2 to 50 pts.mass of conductive powder. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a conductive rubber roller such as a charging roller, a developing roller, or a transfer roller incorporated in a copying machine or a laser beam printer.

  Conventionally, in an electrophotographic image forming apparatus such as a copying machine or a printer, first, the surface of the electrophotographic photosensitive member is uniformly charged, and an image is projected onto the electrophotographic photosensitive member from the optical system so that it is exposed to light. A latent image is formed by erasing the charged part. Next, a method of printing is performed by forming (developing) a toner image by toner adhesion and transferring the toner image onto a recording medium such as transfer paper.

  As a means for uniformly charging the surface of the electrophotographic photosensitive member, a contact for charging the electrophotographic photosensitive member to a predetermined potential by bringing a charging member to which a voltage is applied into contact with the electrophotographic photosensitive member with a predetermined pressing force. A charging method is known. Among the contact charging systems, for example, the charging roller makes uniform contact with the electrophotographic photosensitive member, which is an important point for uniform charging by the contact charging system, between the two rotating cylinders. For this reason, it is easier to implement than other contact charging methods such as brush charging and blade charging, and is adopted.

  Since the charging roller performs contact charging with the electrophotographic photosensitive member, when the charging roller is electrically non-uniform, uneven charging density reflecting the electric non-uniformity is generated. Therefore, the charging roller is required to have a predetermined resistance and be electrically uniform. Further, in order to ensure uniform contact with an electrophotographic photosensitive member or the like, good surface smoothness and high dimensional accuracy are required.

  As such a charging roller, for example, a low hardness conductive rubber layer is provided on the outer peripheral surface of a predetermined conductive shaft body which is a conductor. Furthermore, a resistance adjusting layer and a protective layer are sequentially laminated on the outer peripheral surface of the conductive rubber layer by coating as required.

  By the way, if the conductive rubber roller used as the charging roller is left for a long time in contact with the other member such as the electrophotographic photosensitive member, the conductive rubber roller is permanently deformed at the contact portion with the other member such as the electrophotographic photosensitive member. To do. As a result, the surface of the electrophotographic photosensitive member cannot be uniformly charged, and the image quality deteriorates. In order to form a high-quality image, it is desirable that the conductive rubber roller in contact with another member such as an electrophotographic photosensitive member does not easily be permanently deformed.

  In addition, in order for the conductive rubber roller to uniformly charge other members such as the electrophotographic photosensitive member, high adhesion to the other members is required by reducing the hardness of the conductive rubber layer. Generally, in order to reduce the hardness of the conductive rubber layer, for example, a softener, a plasticizer, or the like is blended with the rubber composition that is the conductive rubber layer material (Patent Document 1). However, oil components such as the softener and plasticizer may ooze out on the surface of the conductive rubber roller and contaminate other members that come into contact therewith.

  The conductive rubber roller is manufactured by extruding a rubber composition into a tube shape, heating and vulcanizing with a vulcanizing can, and press-fitting the tube-shaped rubber to cover the conductive shaft body. There is a way to do it. In addition, there is a method of producing by extruding a coating integral while continuously covering a conductive shaft body with a rubber composition with a crosshead extruder. In the case of the former manufacturing method, since it becomes batch production, it becomes disadvantageous in terms of cost. On the other hand, in the latter manufacturing method, since it is vulcanized in a continuous hot stove, continuous production becomes possible, which is advantageous in terms of cost.

  However, in the crosshead extruder, when the conductive shaft body is coated with a rubber composition having a large swell (shrinkage), the rubber composition contracts from the rubber cut portion (conductive shaft body end), and the conductive shaft There may be a problem of lifting from the body.

  In general, in order to solve the problem of swell (shrinkage) of a rubber composition, there is a method of adding a softener, a plasticizer and the like to impart plasticity to the rubber composition. However, as described above, oil components such as a softener and a plasticizer may ooze out on the surface of the conductive rubber roller and contaminate other members that come into contact therewith.

JP 05-224501 A

  An object of the present invention is to provide a conductive rubber roller that is not easily permanently deformed (low compression set), has low hardness, hardly contaminates other members that come into contact, and has excellent extrudability.

The conductive rubber roller according to the present invention is
In the conductive rubber roller formed by disposing a conductive rubber layer on the outer periphery of the conductive shaft body,
The conductive rubber layer is characterized by using a rubber composition containing the following components (A) to (C).
(A) component: 100 mass parts of rubber component containing at least 0.5-15 mass% of crystalline butadiene resin (B) component: 10-60 mass parts of filler (C) component: 2-50 mass of conductive powder Department.

  The rubber component of the component (A) contains butadiene rubber, and the cis-1,4-bond content of the butadiene rubber is 90% by mass or more.

  The filler of the component (B) is calcium carbonate having an average particle size of 1.0 to 3.0 μm.

  The conductive powder of the component (C) is carbon black.

  According to the present invention, it is possible to provide a conductive rubber roller that is not easily permanently deformed (low compression set), has low hardness, hardly contaminates other members that come into contact, and has excellent extrudability. is there.

It is a perspective view which shows an example of the electroconductive rubber roller which concerns on this invention. It is sectional drawing which shows an example of the extruder used for preparation of the conductive rubber layer in this invention. 1 is a diagram showing a schematic configuration of an image forming apparatus equipped with a process cartridge having a conductive rubber roller according to the present invention.

  Hereinafter, although it demonstrates in detail per form of this invention, this invention is not limited to these.

(Conductive rubber roller)
The conductive rubber roller according to the present invention is a conductive rubber roller in which a conductive rubber layer is disposed on the outer periphery of a conductive shaft. The conductive rubber layer includes the following components (A) to (C): A rubber composition is used.
(A) component: 100 mass parts of rubber component containing at least 0.5-15 mass% of crystalline butadiene resin (B) component: 10-60 mass parts of filler (C) component: 2-50 mass of conductive powder Department.

  An example of the conductive rubber roller according to the present invention is shown in FIG. The conductive rubber roller 1 has a conductive rubber layer 3 on the outer periphery of the conductive shaft 2. The conductive rubber roller 1 may be a conductive rubber roller having a structure of two or more layers by further providing a surface layer or the like on the outer periphery of the conductive rubber layer 3 as necessary.

(Conductive shaft)
As the conductive shaft body in the conductive rubber roller according to the present invention, those used in ordinary rollers can be used without any problem as long as the surface is conductive. For example, rods, pipes, etc. of iron, copper, bronze, stainless steel, cast iron, brass, aluminum, etc. can be used, and those whose surfaces are plated with nickel or the like can also be used. Also, rods, pipes, and resin rods made of a resin composition containing a conductive filler such as carbon black, metal powder, carbon fiber, metal fiber, metal oxide, resin or inorganic powder metallized surface A pipe whose surface is made conductive by metal plating or the like can also be used.

((A) component)
The component (A) contained in the rubber composition is a rubber component containing at least a crystalline butadiene resin. The crystalline butadiene resin refers to a butadiene resin that is easily crystallized, and in the present invention, the n-hexane insoluble matter is used as the crystalline butadiene resin.

  As the rubber component (A), for example, general-purpose rubber such as butadiene rubber, isoprene rubber, styrene butadiene rubber, ethylene propylene diene rubber, acrylonitrile butadiene, or the like can be used as one or two or more kinds of mixed rubber components. . Of these, butadiene rubber is preferred.

  (A) The content rate of the crystalline butadiene resin of a component is 0.5-15 mass%. By setting the content of the crystalline butadiene resin in the above range, it is possible to obtain a conductive rubber roller that suppresses the swell (shrinkage) of the rubber composition during extrusion without impairing the excellent rebound resilience of the rubber component. . Moreover, a conductive rubber roller having a low hardness can be obtained without impairing the original viscosity of the rubber component. However, when the content of the crystalline butadiene resin is less than 0.5% by mass, the swell (shrinkage) of the rubber composition increases during the extrusion process. For this reason, when the conductive shaft body is covered, the rubber composition shrinks from the rubber cut portion (conductive shaft body end portion) and floats up from the conductive shaft body. On the other hand, if the content of the crystalline butadiene resin exceeds 15% by mass, the hardness of the conductive rubber roller increases, making it difficult to satisfy the required characteristics. A preferable content of the crystalline butadiene resin is 3 to 10% by mass. In addition, the content rate of crystalline butadiene resin of (A) component is the value which made n-hexane insoluble matter the amount of crystals.

  Moreover, when the rubber component of the said (A) component contains a butadiene rubber, it is preferable that the cis-1, 4- bond content of this butadiene rubber is 90 mass% or more. By setting it within the above range, a conductive rubber roller excellent in rebound resilience can be obtained. On the other hand, when the cis-1,4-bond content of the butadiene rubber is less than 90% by mass, the crosslinking density of the rubber composition may be reduced, and the rebound resilience of the conductive rubber roller may be reduced. More preferably, the cis-1,4-bond content of the butadiene rubber in the component (A) is 95% by mass or more.

((B) component)
The rubber composition contains a filler (component (B)). In the present invention, the filler refers to a material that functions to improve various properties such as processability or to reduce the cost of the conductive rubber roller. The type of filler is not particularly limited, and examples thereof include calcium carbonate and clay. These may be used alone or in combination of two or more. Among these, calcium carbonate is preferable, and it is particularly preferable to use calcium carbonate having an average particle size of 1.0 to 3.0 μm. By using calcium carbonate having an average particle size of 1.0 to 3.0 μm as the filler, calcium carbonate in the rubber composition is aggregated by kneading, extrusion processing, etc., and the viscosity of the rubber composition is increased. Can be suppressed. Further, when the conductive rubber roller undergoes a polishing process, it is possible to obtain a conductive rubber roller having a smooth surface. However, when the average particle size is less than 1.0 μm, the calcium carbonate tends to aggregate and the viscosity becomes high, so that extrudability and the like may decrease. On the other hand, when the average particle size exceeds 3.0 μm, the surface roughness of the conductive rubber roller after polishing increases, and when the conductive rubber roller is used as a charging roller, other members such as a photoreceptor cannot be charged uniformly. There is a case.

  Further, as the calcium carbonate, heavy calcium carbonate is produced by dry pulverizing the raw stone in the production process, and therefore it is less likely to aggregate during the production process and can be preferably used.

  In addition, the “average particle diameter” in the present specification means a volume average particle diameter calculated from the volume distribution, and can be specifically measured by a laser diffraction method.

  The compounding quantity of (B) component in the said rubber composition is 10-60 mass parts with respect to 100 mass parts of (A) component. By using the rubber composition in the above range, it is possible to suppress swell (shrinkage) of the rubber composition during the extrusion process. Thereafter, when the polishing step is performed, the rubber composition contains the filler, whereby the polishing property is improved and a conductive rubber roller having excellent dimensional accuracy is obtained. However, when the blending amount of the component (B) is less than 10 parts by mass with respect to 100 parts by mass of the component (A), the polishing processability is deteriorated when the polishing process is performed after the extrusion process, and the required dimensional accuracy. Cannot be obtained. On the other hand, when the amount exceeds 60 parts by mass with respect to 100 parts by mass of the component (A), the hardness of the rubber composition increases and the electrical resistance value of the rubber composition increases. Therefore, the required characteristics of the conductive rubber roller It becomes difficult to satisfy. Preferably, the blending amount of the component (B) in the rubber composition is 20 to 50 parts by mass with respect to 100 parts by mass of the component (A).

((C) component)
The rubber composition contains conductive powder for the purpose of imparting conductivity. Examples of the conductive powder as component (C) include carbon black, graphitized carbon black, carbon nanotube, metal, various conductive metal oxides (such as titanium oxide), and the like.

  Among these, carbon black is preferable. The type of carbon black is not particularly limited, and examples thereof include acetylene black, furnace black, “Ketjen black” (trade name, manufactured by Lion Corporation), graphitized carbon black, and the like. Among them, furnace black having a relatively low cost is preferably used. Moreover, there is no restriction | limiting in particular also as an average particle diameter of the said carbon black. However, for example, when furnace black having an average particle diameter of 60 nm or more is used, it may be difficult to impart conductivity to the conductive rubber roller.

The compounding quantity of (C) component in the said rubber composition is 2-50 mass parts with respect to 100 mass parts of said (A) component. Within the above range, the electric resistance value of the rubber composition can be adjusted to 10 ² to 10 ⁸ Ω · cm, which is preferable as a charging roller in an electrophotographic apparatus. Preferably, it is 5-40 mass parts.

(Other ingredients)
In addition to the components (A) to (C), the rubber composition may contain a plasticizer and the like.

(Method for producing conductive rubber roller)
The method for producing a conductive rubber roller according to the present invention will be specifically described below, but is not limited to this method.

  In the method for producing a conductive rubber roller of the present invention, the rubber composition can be extruded by a vent type extruder as shown in FIG. FIG. 2 is a conceptual diagram showing an extruder in the middle of extrusion, and the blacked out portion is a portion filled with a rubber composition.

  A rubber composition is charged from the charging port 11, plasticized by the screw 12, and extruded from the crosshead 14. The crosshead 14 includes a hollow core 14a, and the conductive shaft body 2 is supplied to the crosshead 14 through the core 14a and is coated with a rubber composition. A vent 13 is opened at an intermediate portion of the cylinder 10, and the inside of the cylinder 10 is evacuated by a vacuum pump 15 from here. The vicinity of the vent 13 is adjusted by the shape of the screw 12 so that the rubber composition is not filled. In front of the vent 13 of the screw 12, there is a dam portion 12a in which the depth of the groove is extremely narrowed. By feeding the rubber composition into the cylinder 10 in a vacuum state, the effect of removing moisture is further enhanced.

  After the conductive shaft body 2 is coated with the rubber composition, vulcanization is performed by heating under no pressure. The heating method in the vulcanization step under no pressure is not particularly limited, and examples thereof include heating using an electric heater and heating with a combustion gas. The vulcanization temperature and vulcanization time are not particularly limited, but may be vulcanized at a temperature of about 100 ° C. to 250 ° C. for about 2 minutes to 120 minutes. Then, it grinds so that it may become a desired outer diameter with a grinder, and the electroconductive rubber roller which concerns on this invention can be produced.

(Process cartridge, image forming device)
The process cartridge according to the present invention includes the conductive rubber roller of the present invention. An example of an embodiment of a process cartridge provided with the conductive rubber roller of the present invention as a charging roller is shown in FIG. A process cartridge 30 shown in FIG. 3 includes the conductive rubber roller of the present invention as the charging roller 20. The electrophotographic photosensitive member 22, the exposure means (not shown), the developing means 24, the transfer means 25, the cleaning means 28, etc. are not particularly limited.

  In the process cartridge 30, the electrophotographic photosensitive member 22 is rotationally driven in the direction of the arrow at a predetermined peripheral speed. In the rotation process, the electrophotographic photosensitive member 22 is uniformly charged at a predetermined positive or negative potential on the peripheral surface thereof by the charging roller 20 of the present invention as a primary charging means. Subsequently, the image exposure 23 from image exposure means (not shown), such as slit exposure and laser beam scanning exposure, is received. In this way, electrostatic latent images are sequentially formed on the peripheral surface of the electrophotographic photosensitive member 22.

  The formed electrostatic latent image is then developed with toner by the developing means 24, and the developed toner image is synchronized with the rotation of the electrophotographic photosensitive member 22 between the electrophotographic photosensitive member 22 and the transfer means 25. The transfer unit 25 sequentially transfers the transfer material 26 supplied from a paper supply unit (not shown).

  The transfer material 26 that has received the image transfer is separated from the surface of the electrophotographic photosensitive member 22, introduced into the image fixing means 27, subjected to image fixing, and discharged out of the apparatus as a copy.

  The surface of the electrophotographic photosensitive member 22 after the image transfer is cleaned by the cleaning unit 28 after the transfer residual toner is removed, and used repeatedly for image formation.

  In the above illustration, an example in which the conductive rubber roller of the present invention is used as the charging roller 20 has been shown. However, the conductive rubber roller of the present invention includes a developing roller provided in the developing unit 24, a transfer roller provided in the transfer unit 25, a developer regulating roller provided in contact with the developing roller in the developing unit 24, and the like. Can also be used. Among these, the conductive rubber roller of the present invention can be particularly suitably used as a charging roller.

  The image forming apparatus according to the present invention includes the conductive rubber roller of the present invention. The conductive rubber roller provided in the image forming apparatus can be used not only for the charging roller but also for other roller members, like the process cartridge. The image forming apparatus may incorporate the process cartridge.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited only to these Examples.

Example 1
Butadiene rubber [trade name: “UBEPOL-BR150L”, manufactured by Ube Industries, Ltd., crystalline butadiene resin content: 0 mass%, cis-1,4-bond content: 98 mass%] 60 mass parts butadiene rubber [commodity Name: “UBEPOL-VCR450”, manufactured by Ube Industries, Ltd., crystalline butadiene resin content: 3.8% by mass, cis-1,4-bond content: 98% by mass] 40 parts by mass (the above two types of butadiene (Crystalline butadiene resin content of rubber mixture: 1.5% by mass, cis-1,4-bond content: 98% by mass)
Zinc oxide [trade name: “Zinc Hana 2”, manufactured by Hakusuitec Co., Ltd.] 5 parts by weight Stearic acid [trade name: “Stearic acid S”, manufactured by Kao Corporation] 1 part by weight Calcium carbonate [trade name: “ Super # 1700 ", manufactured by Maruo Calcium Co., Ltd.] 30 parts by mass Carbon black [Product name:"# 5500 ", manufactured by Tokai Carbon Co., Ltd.] 30 parts by mass Dibenzothiazyl disulfide (MBTS) [Product name:" Noxeller DM ", Manufactured by Ouchi Shinko Chemical Co., Ltd.] 1 part by mass Tetramethylthiuram monosulfide (TMTM) [trade name:" Noxeller TS ", manufactured by Ouchi Shinko Chemical Co., Ltd.] 1 part by mass Sulfur [trade name: “Salfax PMC” manufactured by Tsurumi Chemical Co., Ltd.] 0.8 parts by mass.

  The above compounds were kneaded to prepare an unvulcanized conductive rubber composition. Next, the unvulcanized rubber composition is put into an extruder with a φ70 crosshead die, extruded together with a conductive shaft pre-applied with an adhesive so that the outer diameter is about φ13 mm, and placed on the outer periphery of the conductive shaft. The unvulcanized rubber composition was coated. At this time, the extrusion speed of the rubber was continuously supplied at a constant speed of the screw rotation speed of 14 rpm and the conductive shaft feed speed of 2.5 m / min. The inner diameter of the conductive shaft guide in the cross head was 6.1 mm. This molded body was vulcanized in an electric furnace at 170 ° C. for 1 hour, and set in a polishing machine equipped with a polishing grindstone GC80. Grinding was performed so that the outer diameter was 12 mm at a rotational speed of 2000 rpm and a feed speed of 0.3 m / min, and a conductive rubber roller was produced.

(Example 2)
Instead of the two types of butadiene rubber,
Butadiene rubber [trade name: “UBEPOL-VCR412”, manufactured by Ube Industries, Ltd., crystalline butadiene resin content: 12.0% by mass, cis-1,4-bond content: 98% by mass] 100 parts by mass The procedure was the same as in Example 1 except that there was.

(Example 3)
Instead of the two types of butadiene rubber,
Butadiene rubber [Brand name: “UBEPOL-BR150L”, manufactured by Ube Industries, Ltd.] 80 parts by mass Butadiene rubber [Brand name: “UBEPOL-VCR450”, manufactured by Ube Industries, Ltd.] 20 parts by mass (the above two types of butadiene (Crystalline butadiene resin content of rubber mixture: 0.8% by mass, cis-1,4-bond content: 98% by mass)
The same procedure as in Example 1 was performed except that was used.

Example 4
Instead of the calcium carbonate and carbon black,
Except for using 60 parts by mass of carbon carbonate [trade name: “Super # 1700”, manufactured by Maruo Calcium Co., Ltd.] 40 parts by mass of carbon black [trade name: “# 5500”, manufactured by Tokai Carbon Co., Ltd.] Performed as in Example 1.

(Example 5)
Instead of the calcium carbonate and carbon black,
Except for using 10 parts by mass of carbon carbonate [trade name: “Super # 1700”, manufactured by Maruo Calcium Co., Ltd.] 25 parts by mass of carbon black [trade name: “# 5500”, manufactured by Tokai Carbon Co., Ltd.] Performed as in Example 1.

(Comparative Example 1)
Instead of the two types of butadiene rubber,
Butadiene rubber [trade name: “UBEPOL-BR150L”, manufactured by Ube Industries, Ltd.] 90 parts by mass Butadiene rubber [Product name: “UBEPOL-VCR450”, manufactured by Ube Industries, Ltd.] 10 parts by mass (the above two types of butadiene Crystalline butadiene resin content of rubber mixture: 0.4% by mass, cis-1,4-bond content: 98% by mass)
The same procedure as in Example 1 was performed except that was used.

(Comparative Example 2)
Instead of the two types of butadiene rubber,
Butadiene rubber [trade name: “UBEPOL-VCR617”, manufactured by Ube Industries, Ltd., crystalline butadiene resin content: 17.0% by mass, cis-1,4-bond content: 98% by mass] 100 parts by mass The procedure was the same as in Example 1 except that there was.

(Comparative Example 3)
Instead of the calcium carbonate and carbon black,
Except for using 70 parts by mass of carbon carbonate [trade name: “Super # 1700”, manufactured by Maruo Calcium Co., Ltd.] 30 parts by mass of carbon black [trade name: “# 5500”, manufactured by Tokai Carbon Co., Ltd.] Performed as in Example 1.

(Comparative Example 4)
Instead of the calcium carbonate and carbon black,
Calcium carbonate [trade name: “Super # 1700”, manufactured by Maruo Calcium Co., Ltd.] 5 parts by mass Carbon black [trade name: “# 5500”, manufactured by Tokai Carbon Co., Ltd.] 25 parts by mass Performed as in Example 1.

(Micro hardness MD-1 evaluation)
The micro hardness of the obtained conductive rubber roller was measured in a 23.5 ° C./60% RH environment using a hardness measuring instrument “Micro hardness meter MD-1 type” (trade name, manufactured by Kobunshi Keiki Co., Ltd.). did. As a measuring method, a conductive rubber roller was placed on a metal plate, and was easily fixed by a metal block so that the conductive rubber roller did not roll. The measurement terminal was made to accurately contact the center of the conductive rubber roller from the direction perpendicular to the metal plate, and the value shown in the peak hold mode was read. In addition, a total of 9 locations were measured at a location (2 locations) 30 mm from the edge of the coating layer of the conductive rubber roller and 3 locations each in the circumferential direction, and the average value of the measured values obtained was measured for the conductive rubber roller. The micro hardness was used.

(Extruded shape evaluation)
The end shape of the 50 conductive rubber rollers obtained was visually observed, and it was examined whether or not the rubber composition at the end floated from the conductive shaft. The case where no lifting from the conductive shaft body was confirmed was evaluated as “○”, and the case where lifting was confirmed was evaluated as “×”.

<Image evaluation>
A surface layer as shown below was applied to a conductive rubber roller ground to an outer diameter of φ12 mm obtained using the rubber compositions of Examples and Comparative Examples.
・ Acrylic polyol solution (trade name: “PLACCEL DC2016”, manufactured by Daicel Chemical Industries)
(Contains 70% by mass of active ingredient and 30% by mass of xylene as a diluent solvent) 100 parts by mass / isocyanate A (IPDI) (trade name: “VESTANAT B1370”, manufactured by Degussa)
(60% by mass of active ingredient, 15% by mass of n-butyl acetate and 25% by mass of xylene as dilution solvent) 40 parts by mass / isocyanate B (HDI) (trade name: “DURANATE TPA-B80E”, manufactured by Asahi Kasei Chemicals )
(Contains 80% by mass of active ingredient and 20% by mass of ethyl acetate as diluent) 30 parts by mass / carbon black (trade name: “CS-Bk100Y”, manufactured by Toda Kogyo Co., Ltd.) 30 parts by mass / surface-treated titanium oxide (trade name) : "SMT-150IB", manufactured by Teica) 25 parts by mass PMMA resin particles (trade name: "MAX-12", manufactured by Sekisui Plastics Co., Ltd.) 50 parts by mass, modified dimethyl silicone oil (trade name: "SH28PA" 0.08 parts by mass. 400 parts by mass of methyl isobutyl ketone.

  The above compound was stirred using a mixer to prepare a mixed solution. Subsequently, the mixed solution was subjected to dispersion treatment (treatment speed 500 ml / min) using a circulation type bead mill disperser to prepare a dip coating paint. The viscosity of this paint was 8.0 mPas.

  The following evaluation was performed on the conductive rubber roller obtained as described above.

(C-SET evaluation)
The conductive rubber roller was mounted on an electrophotographic apparatus (trade name: “HP Color LaserJet 3000”, manufactured by Hewlett-Packard Company) as a charging roller. After leaving in a harsh environment of 40 ° C. and 95% RH for one month, returning to the environment of 23 ° C. and 53% RH, and quickly outputting a halftone image with a printer, the output image has a contact mark with the image forming body. I checked whether it appeared. The case where no contact trace appeared was evaluated as ◯, and the case where the contact trace could be confirmed was evaluated as ×.

(Photosensitive drum surface evaluation)
After the C-SET evaluation, the photosensitive drum was taken out from the electrophotographic apparatus, and the presence or absence of contamination on the photosensitive drum surface was confirmed with a laser microscope. The case where contamination was not confirmed on the surface was marked with ◯, and the case where contamination was confirmed on the surface was marked with ×.

  The evaluation results are shown in Table 1. In addition, the unit of the compounding quantity of each raw material is a mass part.

  As is clear from the above results, the conductive rubber rollers produced in Examples 1 to 5 are not easily permanently deformed (low compression set), have low hardness, hardly contaminate other members that come into contact, and are extruded. It turns out that the property is excellent.

  On the other hand, in Comparative Example 1, since the crystalline butadiene resin content is low, the hardness decreases. However, swell (shrinkage) increases during extrusion. For this reason, when the rubber material was coated on the conductive shaft body, the rubber material contracted from the rubber cut portion (conductive shaft body end portion) and lifted from the conductive shaft body. Moreover, compression set became large and the contact trace with the other member was confirmed.

  In Comparative Example 2, since the crystalline butadiene resin content was high, the hardness was high, and the pressure in the extruder during extrusion was high. For this reason, the rubber material was not uniformly coated on the conductive shaft, and the rubber material was lifted from the conductive shaft.

  In Comparative Example 3, since the amount of calcium carbonate was large, the compression set was increased, and contact marks with other members were confirmed.

  In Comparative Example 4, since the amount of calcium carbonate is small, the swell (shrinkage) becomes large during the extrusion process, and when the rubber material is coated on the conductive shaft, the rubber cut portion (conductive shaft end) The rubber material shrunk and floated from the conductive shaft.

  As described above, according to the present invention, it is possible to provide a conductive rubber roller that is not easily easily permanently deformed (low compression set), has low hardness, hardly contaminates other members that come into contact, and has excellent extrudability. Is possible.

DESCRIPTION OF SYMBOLS 1 Conductive rubber roller 2 Conductive shaft 3 Conductive rubber layer 10 Cylinder 11 Slot 12 Screw 12a Dam part 13 Vent 14 Cross head 14a Core 15 Vacuum pump 20 Charging roller 21 Power supply 22 Electrophotographic photosensitive member 23 Image exposure 24 Development Means 25 Transfer means 26 Transfer material 27 Image fixing means 28 Cleaning means 29 Rail 30 Process cartridge

Claims (4)

In the conductive rubber roller formed by disposing a conductive rubber layer on the outer periphery of the conductive shaft body,
The conductive rubber layer is a conductive rubber roller using a rubber composition containing the following components (A) to (C).
(A) Component: 100 parts by mass of rubber component containing at least 0.5-15% by mass of crystalline butadiene resin (B) Component: 10-60 parts by mass of filler (C) Component: 2-50 masses of conductive powder Department.   2. The conductive rubber roller according to claim 1, wherein the rubber component of the component (A) contains butadiene rubber, and the cis-1,4-bond content of the butadiene rubber is 90% by mass or more.   The conductive rubber roller according to claim 1, wherein the filler of the component (B) is calcium carbonate having an average particle diameter of 1.0 to 3.0 μm.   4. The conductive rubber roller according to claim 1, wherein the conductive powder of the component (C) is carbon black.

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